High sensitivity and optimum design of LSPR-based sensors by coupled nano-rings for cancer detection

Abstract

Plasmonic RI sensors are widely used in various fields due to their high sensitivity and specificity; and is based on the change of the refractive index of the system. In this research work, we investigate an LSPR-based sensor consisting of two coupled silver nano-rings on a SiO2/Si substrate. The sensor's sensitivity, full width at half maximum (FWHM), and figure of merit (FOM) of the sensor are measured to be 393.14 nm/RIU, 53.2 nm, 7.39 RIU−1, respectively. The resonance peak is generated by the focused electric field in the elliptical area between the nano-rings. By assuming an etched area filled with the solution under the elliptical area between the nano-rings, we enhance the interaction between the solution and the penetrated electrical field in the SiO2 layer. This approach increases the sensitivity, FWHM, and FOM to 524.3 nm/RIU, 52.3 nm, 10.024 RIU−1, respectively. The designed sensor as a bio-sensor is capable of effectively detecting different types of cancerous cells from healthy cells, since the refractive index of a cell that affected by cancer, is higher than healthy cell. The simulation results show good selectivity for each type of cancer, with a FOM of approximately 9.5 RIU−1.